With reference to FIG. 1, a block diagram of a conventional wastewater treatment process is shown. The treatment includes influent wastewater 111 being settled in a primary settling basin 110. Settled sludge 115 (i.e., primary sludge) is sent to an anaerobic sludge digester 140, while the settled wastewater 112 is sent for secondary treatment. This secondary treatment may include biological aeration in aeration tanks 120 and a final settling process in a final settling basin 130. A portion of the sludge 114 from the final settling basin 130 is returned to the secondary treatment in order to maintain biological compounds in the influent. Effluent water stream 118 that meets water quality standards is output from the final settling basin 130. The remainder of the waste activated sludge 113 from the final settling basin 130 is sent to the anaerobic sludge digester 140. After the anaerobic sludge digestion process, the removed water 116 is mixed with the incoming influent wastewater 111 and the stabilized solids (biosolids) 117 are now safe for application as fertilizers, for example.
One problem that plagues conventional wastewater treatment plants is nitrogen removal to meet effluent discharge water quality standards. There are various sources of nitrogen in municipal wastewater, including human feces, industrial wastes, and other garbage. Typically, nitrogen removal at wastewater treatment plants is achieved by a series of nitrification and denitrification steps. Specifically, nitrifying bacteria convert ammonia to nitrite and subsequently to nitrate, followed by denitrification of nitrite or nitrate to nitrogen gas. The general chemical equations for these processes are:

The capability to remove nitrogen is constrained by the rate limiting aerobic nitrification reactions to convert ammonia to nitrite and/or nitrate by slow growing autotrophic organisms. The cumulative volume requirements for nitrogen removal depends on the completion of these reactions. Accordingly, there is a need and desire for a more efficient nitrogen removal process by encouraging the nitrification/denitrification processes in the mainstream reactor.